Field
The invention relates to an instrument guide assembly for a bone plate and a kit including a bone plate and such an instrument guide assembly. The instrument guide assembly includes an insert configured to be placed into a hole of a bone plate and a guide member that provides guidance for a drill bit, a guide wire, or an instrument which is used, for example, for the correct placement of the bone plate. The insert and the guide member can be connected to each other in a manner that prevents or reduces a possibility of losing the components. The instrument guide assembly is particularly useful for a bone plate that facilitates a polyaxial coupling between a bone anchor and a plate member of the bone plate.
Description of Related Art
EP 1 878 394 A2 describes an orthopaedic fixation plate system including a fixation plate including a hole with a spherically-curved inner surface and a polyaxial bushing provided in the hole. A removable guide is provided in the polyaxial bushing. The polyaxial bushing permits the surgeon to modify the angle of each guide and bushing to a selected orientation before locking the bushing at an orientation by tightening the guide into the bushing.
As generally known, for a bone plate that allows for a polyaxial coupling between a bone anchor and a plate member, it is necessary that a ball-shaped portion of the bone anchor lines up exactly with a ball-shaped seat in the plate member. Misalignment of the ball-shaped portion of the bone anchor and the ball-shaped seat in the plate member may cause stresses in the bone and may prohibit correct function of the bone plate.
WO 2012/046210 A1 describes a bone plate assembly including a plate member with at least one hole extending from a top side to a bottom side of the plate member, an insert arranged in the hole, the insert having a through-hole, and a guide member removably arranged in the through-hole of the insert, the guide member having a guide channel and an outer surface portion which engages an inner wall portion of the through-hole to allow an adjustment of an angular orientation of the guide member within the insert and relative to the plate member.